1. Field of the Invention
The present invention relates to a storage apparatus, a method of controlling the amount of write current overshoot in a storage apparatus, and a storage medium storing its program and, more particularly, to a storage apparatus, a method of controlling the amount of write current overshoot in a storage apparatus, and a storage medium storing its program capable of controlling a write current and the amount of its overshoot to an optimum value which are proposed as a technique relating to record control, read control of an HDD that has recently been used in various types of products such as a desktop PC, notebook PC, server, audio-visual equipment, and automobile product, and reliability of the HDD.
2. Description of the Related Art
Along with improvement in the recording density (surface density) of HDD, linear density (BPI)/transfer rate is improved. In such a circumstance, improvement of write performance is also demanded. In order to enhance the write performance at a higher linear density and a higher transfer rate, rise- and fall-speed of a write current needs to be increased as well as current to be supplied needs to be increased.
However, the rise- and fall-speed are substantially determined by the characteristic of a PreAmplifier IC (Pre Amp) and set write current. Further, with regard to the Pre Amp, one that has an auxiliary function of determining the rise and fall characteristic, i.e., a function of controlling the amount of overshoot at the rise time of the write current, becomes popular.
Under the above situation, control of write current overshoot that influences the write performance has been widely demanded.
For example, there is known a method of controlling a write current comprising: a step that checks error rate while changing recording parameters under a test condition corresponding to the operating temperature of a disk drive; a step that selects a recording parameter value exhibiting the lowest error rate, and a step that uses a recording parameter value selected under an operating environment to optimize recording current of the disk drive (refer to, e.g., Patent Document 1 (Jpn. Pat. Appln. Laid-Open Publication No. 2004-199860)).
In the prior art disclosed in the Patent Document 1, the minimum write current and overshoot current (OSC) that fall within the limit of ensuring the head recording performance and that exhibit lowest error rate are used. In this case, if there exist two or more minimum values, a normalization technique is used.
However, such a control method of selecting the minimum value of current parameters cannot reflect the entire operating characteristics, thus posing a problem in terms of maintenance of reliability against a change in use environment, aged deterioration, and the like.